But the technology developed at the Wyss Center for Bio and Neuroengineering in Geneva will hopefully just be a first step.

At present, the technology only allows patients to respond to simple yes/no questions posed by people around them.

But Professor Niels Birbaumer, one of the scientists who developed the technique, said that the next step would be to allow patients to come up with their own questions by selecting letters and words from an alphabet.

With lots of training by the patients and the computer software that interprets the brain activity, perhaps locked-in patients will one day be able to communicate freely with family and carers.

Dr Srivas Chennu, a computer scientist from the University of Kent who works with patients in a minimally conscious or vegetative state, said that the the more information doctors and scientists could get about the thinking or moods of their patients, the more those patients could have a say in their care.

Even if their mode of communication was nowhere near as complex as a normal conversation, it would be immeasurably helpful.

Those tantalising ideas are still many years away from reality, according to Prof Birbaumer.

It’ll take several more technological steps and will most likely need electrodes implanted into the brain, to read a patient’s thoughts more precisely than is possible with the optical sensors used until now by the Wyss Center team.

But that is the remarkable direction in which this profound work is heading.